jxl.write.WritableWorkbook 不支持多线程

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jxl.write.WritableWorkbook 不支持多线程0

在使用 jxl.write.WritableWorkbook 将数据导出成excel文件的过程中，发现在继承 Thread 类生成的excel中并没有数据（在查询的时候是有数据的）。

如果将类 UserExcelExport 声明为不继承 Thread，导出的excel中是有数据的。
这是什么一回事呢？

代码如下：

action:

public void exportUserTest() {

		LOG.info("start to export userTest.");
		// 获取查询表单中的查询条件
		String userName = (String) getSearchValue().get("userName");
		userName = userName == null ? null : userName.trim();

		StringBuffer sqlBuf = new StringBuffer(
				"select * from user_test where 1=1 ");

		if (null != userName && !"".equals(userName)) {
			sqlBuf.append(" and USER_NAME like '%" + userName + "%'");
		}

		LOG.info("search condition: userName=" + userName);

		List<UserTest> list = null;
		try {
			list = userTestService.queryList(sqlBuf.toString());
		} catch (Exception e) {
			LOG.error("query usertest list fail!", e);
		}

		String[] head = new String[] { "用户ID", "用户名", "年龄", "注册时间" };

		HttpServletResponse resp = ServletActionContext.getResponse();
		OutputStream os = null;
		try {
			os = resp.getOutputStream();
			String name = "用户信息";
			resp.reset();
			byte[] fileNameByte = (name + ".xls").getBytes("GBK");
			String fileName = new String(fileNameByte, "ISO8859-1");
			resp.setHeader("Content-disposition", "attachment; filename="
					+ fileName);
			resp.setContentType("application/msexcel");

			UserExcelExport export = new UserExcelExport(os, name, head, list);
			
			Thread thread = new Thread(export);
			
			thread.start();

		} catch (IOException e) {
			LOG.error("get OutputStream faile!", e);
		} catch (Exception e) {
			LOG.error("export usertest fail!", e);
		} finally {
			try {
				if (null != os) {
					os.close();
				}
			} catch (IOException e) {
				LOG.error("close OutputStream faile!", e);
			}
		}

		LOG.info("end to export userTest.");
	}

导出excel的类

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;

import org.apache.log4j.Logger;

import jxl.Workbook;
import jxl.write.WritableFont;
import jxl.write.WriteException;
import jxl.write.biff.RowsExceededException;

public class UserExcelExport extends Thread {
	
	private static Logger log = Logger.getLogger(UserExcelExport.class);

	private OutputStream _os;
	private String _subject;
	private String[] _titles;
	private List<?> _list;

	public UserExcelExport() {
	}

	public UserExcelExport(OutputStream os, String subject, String[] titles,
			List<?> list) {

		this._os = os;
		this._subject = subject;
		this._titles = titles;
		this._list = list;
	}

	public void run() {

		createOutPutStreamForObjs(_os, _subject, _titles, _list);
	}

	public void createOutPutStreamForObjs(OutputStream os, String subject,
			String[] titles, List<?> list) {
		
		jxl.write.WritableWorkbook wwb = null;
		try {
			wwb = Workbook.createWorkbook(os);
			int number = 0;
			int num = 50000;

			while ((number + 1) * num <= list.size()) {
				jxl.write.WritableSheet ws = wwb.createSheet(subject + number,
						number);

				// 表格头
				// 添加带有字型Formatting的对象
				jxl.write.WritableFont wfTitle = new jxl.write.WritableFont(
						WritableFont.TAHOMA, 12, WritableFont.BOLD, false);
				jxl.write.WritableCellFormat wcfFTitle = new jxl.write.WritableCellFormat(
						wfTitle);
				for (int i = 0; i < titles.length; i++) {
					jxl.write.Label labelCFTitle = new jxl.write.Label(i, 0,
							titles[i], wcfFTitle);
					ws.addCell(labelCFTitle);
				}

				// 表格内容
				jxl.write.WritableFont wf = new jxl.write.WritableFont(
						WritableFont.TAHOMA, 11, WritableFont.NO_BOLD, false);
				jxl.write.WritableCellFormat wcfF = new jxl.write.WritableCellFormat(
						wf);
				int numI = 0;
				for (int i = number * num; i < (number + 1) * num; i++) {
					Object[] subList = (Object[]) list.get(i);
					for (int j = 0; j < subList.length; j++) {
						String text = subList[j] == null ? "" : subList[j]
								.toString();
						jxl.write.Label labelCF = new jxl.write.Label(j,
								numI + 1, text, wcfF);
						ws.addCell(labelCF);
					}
					numI++;
				}
				number = number + 1;
			}

			if (list.size() > number * num) {
				jxl.write.WritableSheet ws = wwb.createSheet(subject + number,
						number);

				// 表格头
				// 添加带有字型Formatting的对象
				jxl.write.WritableFont wfTitle = new jxl.write.WritableFont(
						WritableFont.TAHOMA, 12, WritableFont.BOLD, false);
				jxl.write.WritableCellFormat wcfFTitle = new jxl.write.WritableCellFormat(
						wfTitle);
				for (int i = 0; i < titles.length; i++) {
					jxl.write.Label labelCFTitle = new jxl.write.Label(i, 0,
							titles[i], wcfFTitle);
					ws.addCell(labelCFTitle);
				}

				// 表格内容
				jxl.write.WritableFont wf = new jxl.write.WritableFont(
						WritableFont.TAHOMA, 11, WritableFont.NO_BOLD, false);
				jxl.write.WritableCellFormat wcfF = new jxl.write.WritableCellFormat(
						wf);
				int numI = 0;
				for (int i = number * num; i < list.size(); i++) {
					Object[] subList = (Object[]) list.get(i);
					for (int j = 0; j < subList.length; j++) {
						String text = subList[j] == null ? "" : subList[j]
								.toString();
						jxl.write.Label labelCF = new jxl.write.Label(j,
								numI + 1, text, wcfF);
						ws.addCell(labelCF);
					}
					numI++;
				}
			}
			// 写入Exel工作表
			wwb.write();

		} catch (RowsExceededException e) {
			log.error("RowsExceededException.", e);
		} catch (FileNotFoundException e) {
			log.error("FileNotFoundException.", e);
		} catch (WriteException e) {
			log.error("WriteException.", e);
		} catch (IOException e) {
			log.error("IOException.", e);
		} catch(Exception e){
			log.error("Others Exception.", e);
		}finally {
			// 关闭Excel工作薄对象
			try {
				if (wwb != null) {
					wwb.close();
				}
				if (null != os) {
					os.close();
				}
			} catch (WriteException e) {
				log.error("WriteException.", e);
			} catch (IOException e) {
				log.error("IOException.", e);
			}
		}
	}
}

Excel